Making Furniture from Air-Dried Oak?

A beginner asks about drying wood for use in rustic furniture. April 20, 2011

I am very new to wood working and have learned on my own for the most part. I don't know a lot of the terms used on this forum. With that said here is my question. Can I build with oak that has been air dried or does it have to be kiln dried? I live in WI and the furniture I plan to make with the oak (red) will stay here when finished, if that matters.

The oak has been drying for two years and it has been covered. The ends were not sealed. I read that that could cause checking? What is checking and how can I look for it? I can buy this air dried oak for $2 a bf. rough 4/4 or should I buy from a local saw mill kiln dried for $3 a bf 4/4 or finished on 3 sides 3/4 for $3.50 a bf.?

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
After air drying this long, your moisture is likely between 16 - 12% MC. In the wintertime, furniture will reach 6% MC. So, you are looking at a 6%-10% MC change, which with oak is about 2 to 3% shrinkage. You need to reduce the moisture further by putting the lumber someplace warm and dry - attic, kiln, warm and dry room, etc. Kiln drying does offer the advantage of killing any insects. It is faster and more uniform perhaps.

From contributor J:
Checking is a specific sort of cracking caused by uneven shrinkage. When the ends of a board or log are left unsealed, they dry and shrink faster than the middle of the board/log, and the wood typically develops cracks in those unsealed ends. These cracks typically follow radial lines (along lines radiating out from the center of the tree). It doesn't ruin the whole board, but it can force you to scrap up to a foot or so off each end.

The shrinkage that will occur in this air-dried wood after it's brought into a climate-controlled environment won't necessarily be a deal-breaker for you; just don't expect boards to stay flat and joints tight. $2/BF sounds rather steep for red oak that's simply been sitting under cover for a couple of years. It's surely not a bargain price.

From the original questioner:

To contributor J: when you say not to expect the boards to stay flat and joints tight are you talking about reclaimed wood or the air dried oak?

From contributor J:
I'm talking about any wood that is wetter when you make the object than it will be in use. The air-dried wood will definitely move as it adjusts to an indoor environment. The reclaimed wood is harder to predict, since I have no idea how it was recently stored.

From contributor H:
I live in northern WI and our climate is the most extreme from high humidity to drier than dry. The wood will move all around if not kiln dried. I wouldn't be paying $2/ b.f for air dry. Kiln dry sel and better is only bringing $1.50- &1.85/ b.f/.

From contributor N:
Kiln dried wood will move also. Maybe not quite as much as air dried. When building things plan on the wood moving from season to season. I mostly air dry mine then put it in a small room with a dehumidifier running in the summer and heated in the winter that gets my wood down to 6% when needed.

From contributor P:
To answer the original question, yes you can build with air dried lumber. All lumber will move as it absorbs moisture from its surroundings or when the surroundings become very dry. So if it's kiln dried or air dried, it will always move until it reaches it equilibrium point where it will then become stable.

All of my lumber for the past four years has been air dried and thus all my furniture has been built with air dried lumber. All the lumber I used in the previous ten years before I got my own mill was air dried. I have not had any problems with any of the furniture I built either for myself or for my customers.

I typically leave my lumber outdoors, covered for as much as two months, then I bring the lumber into my shop for at least another month or two before I even use it. Often times, it sits in my shop for a year before I use it. Each species takes a different amount of time to dry and it also depends greatly on your location and time of year so your location might be different. Here in the Northeast, I cut in the spring and fall. Drying takes less time in the summer than in the winter.

There is always checking at the ends. Checking are cracks propagating horizontally from the ends of the boards, and yes I just cut that off. I don't mind the loss because I mill my own lumber. My customers don't mind the loss because I sell all my lumber at $1/board foot regardless of type or quality. Even quartersawn lumber, which is the only way I cut oak, is only $1/bdft.

Check out the photo below, these pieces were made with lumber that ranged from 9% to 12% moisture content. I still use these pieces of furniture everyday and I have not had any problems.

Click here for higher quality, full size image

From the original questioner:
I have some walnut that is air drying and I was beginning to think I wasn’t going to be able to use it. To be honest I am still a little afraid to use air dried for customer work. I guess I will use it for my own use until I gain more experience. I think more of the guys that replied lean towards kiln drying. I would rather be safe than sorry. $1 a board foot is very tempting though. I just found someone that has a lot of air died lumber for that price and he is nearby.

From contributor P:
I did some research at one point, and if I remember correctly, most people were using air dried lumber for commercial products right up until the 1990s. That's when kiln dried became more of the norm. I build Shaker furniture. The Shaker's built all the furniture from air dried material and 100s of years later, much of it still exists.

To be honest, I still feel the need to leave my lumber in my shop where the temperature is a typical 75 degrees and the dehumidifier keeps the moisture down to around 45%. After sitting in my shop for a while it's more than stable enough to use. Of course, since I have so much lumber of my own, what I bring into my shop now, probably won't be used for another year.

Too many people in this world aren't used to waiting. This world is too rushed and people need to learn to plan ahead. I see internet prices for quarter sawn red oak, kiln dried, for around $4 to $6 /bdft. If I can get it for $1/bdft but have to wait a year to use it, it's worth the wait time.

From Gene Wengert, forum technical advisor:
It is not necessary to kiln dry, but it is necessary to dry further than the MC level achieved in air drying (12% MC would be possible with really long drying times). Kiln drying at over 140 F offers the opportunity to set the pitch, achieve uniform final MC’s, kill any insects, and is rapid.

From contributor A:
Time is money and money is time. When you have time you most often have no money. Kiln drying does not really add that much cost to a board. So for your 1x6x8' board that you are charging $4.00 for would only be $4.80 if you kiln dried it. Also you would have less money in inventory then in the kiln if you use much wood at all.

A lot of the old furniture you are talking about was made well and taken care of and was most often made from q-sawn wood as it is more stable. Old homes did not have ac systems and though wood heat dried out a house they had a lot more drafts to soften the change of MC.

I timber frame with green and air dried wood all the time. There are tricks to doing this. Also build bent wood chairs from green ash that is steamed then bent to shape. While the rest of the chair may be kiln dried the back is just steamed.

From Gene Wengert, forum technical advisor:
If you drill a hole in wetter wood, as the wood dries, the hole will shrink; actually, the wood around the hole shrinks, which makes the hole smaller. So, with the legs of a chair, a bit of wetness was good because then when the dry tenon or dowel was put into the hole, the wood joint automatically got really tight.

From contributor G:
They used to make chairs out of fairly wet wood for the chair bottom, and the legs and back supports would be from very dry round pieces. When it was put together, the tenons for the legs and back would be put into very hot dry sand before being placed in the hole. Thus, the legs/back tenons would swell with the addition of moisture and the bottom holes would shrink due to the loss of moisture. This would make a very tight joint which would last for a long time without glue, etc.

Wood shrinks as it losses moisture and grows as it gains moisture. I make furniture with primarily air dried wood but allow for the expansion/contraction of wood when building it. Even when I use kiln dried (often) it may be 10% MC or more if it was stored in an unheated building. There are several programs on this site where you can calculate the amount of wood movement using existing moisture content. If you use wood that has 12% MC to build furniture, allow enough contraction for it to be used at 6-8% MC. which is what most modern homes experience in the winter.